Oxidative dehydrogenation process

ABSTRACT

AN OXIDATIVE DEHYDROGENATION PROCESS WHEREIN A TIN/ PHSOPHROUS/OXYGEN/GROUPS IA OR IIA IS IMPREGNATED WITH ADDITIONAL TIN AND THEN IS HEATED TO IMPROVED THE PHYSICAL INTEGRITY OF THE CATALYST.

UnitcclStates Patent Oflice 3,830,869 Patented Aug. 20, 1974 3,830,869OXIDATIVE DEHYDROGENATION PROCESS Emory W. Pitzer, Bartlesville, kla.,assignor to Phillips Petroleum Company No Drawing. Original applicationJune 22, 1970, Ser. No. 48,543, now Patent No. 3,687,868. Divided andthis application June 19, 1972, Ser. No. 264,152

Int. Cl. C07c /18 US. Cl. 260-680 E 16 Claims ABSTRACT OF THE DISCLOSUREAn oxidative dehydrogenation process wherein a tin/ phosphorus/oxygen/Groups Ia or Hz: is impregnated with additional tin and then is heatedto improve the physical integrity of the catalyst.

This application is a division of application Ser. No. 48,543, filedJune 22, 1970, now Pat. No. 3,687,868.

This invention relates to an improved oxidative dehydrogenationcatalyst. In another aspect, this invention relates to a process for theproduction of an improved oxidative dehydrogenation catalyst.

Heretofore, oxidative dehydrogenation catalysts have been formed fromphosphoric acid and tin oxide. These catalysts were improved by formingthe oxidative dehydrogenation catalysts from a phosphorus-containingmaterial, a tin-containing material, and a Group Ia or Ila metal ormetal-containing material, see copending application Ser. No. 810,831,filed on Mar. 26, 1969, now abandoned.

It now has been found that these oxidative dehydrogenation catalysts areimproved by heating the catalysts, impregnating the heated catalystswith tin or a tin-containing material to provide the catalysts with 0.25to 10 weight percent of additional tin based on the weight of theinitial catalyst, and heating the thus-treated catalysts.

The process of this invention provides a novel catalyst with improvedphysical integrity, i.e., improved physical strength. Such a catalystwill have a longer life in conventional catalytic reactors. Further, thethus-treated catalyst is less susceptible to pulverization duringhandling or shipping.

The thus-treated catalyst is useful for oxidatively dehydrogenating avariety of hydrocarbons, for example, olefins such as alkenes, andcycloalkenes and the like.

Accordingly, it is an object of this invention to provide a process forthe production of an oxidative dehydrogenation catalyst.

Another object of this invention is to provide an oxidativedehydrogenation catalyst.

Other objects, aspects and advantages of this invention will becomeapparent to one skilled in the art upon consideration of the disclosureand appended claims.

Substantially any phosphorus, tin, and Group Ia or Ila containingmaterials can be employed in preparing the catalyst to be treatedaccording to this invention so long as at least one of the materialsused contains oxygen, none of the materials is deleterious todehydrogenation catalytic effects, and all of the elements in thematerials used other than phosphorus, tin, oxygen, and Group Ia or Ilametals are volatilized by heating the catalysts to at least thetemperature at which the catalyst is used, e.g., 1000 F., or are removedby washing the catalyst, e.g., with water.

Suitable phosphorus-containing materials employed to prepare thecatalyst include, besides phosphoric acid, phosphorus pentoxide, thephosphorus halides, and the Group la or Ila metal phosphates such aslithium phosphate, sodium phosphate, potassium phosphate, rubidiumphosphate, cesium phosphate, magnesium phosphate, calcium phosphate, andthe like. Other phosphorus-containing materials that can be employed toprepare the catalyst to be treated according to this invention areammonium phosphate and monoand dibasic phosphates of ammonia and ofGroup Ia and IIa metals such as lithium monobasic phosphate, sodiumdibasic phosphate, beryllium dibasic phosphate, magnesium dibasicphosphate, barium monobasic phosphate, ammonium phosphate, ammoniumdibasic phosphate, and the like.

The tin materials employed to prepare the catalysts to be treatedaccording to this invention include any such material soluble ordispersable in water, alcohol, or ether, and include both stannous orstannic compounds. Representative examples of suitable tin compoundsare, for sake of brevity, given only as the stannic compound but it isto be understood that the corresponding stannous compound is equally asapplicable. Representative examples include stannic halides (stannicfluoride, stannic chloride, stannic bromide, stannic iodide), stannicsulfate, stannic acetate, stannic oxide, stannic tartrate, and stannicnitrate. The tin materials employed to prepare the catalyst to betreated according to this invention and in the impregnation step can bethe same or different tin compound.

Besides elemental Group Ia or IIa metals, Group Ia or IIametal-containing materials that can be used include the nitrates, thehalides, the sulfates, the oxalates, the acetates, the carbonates, thepropionates, the tartrates, the bromates, the chlorates, the oxides, thehydroxides, and the like.

The phosphorus-containing materials, the tin-containing materials, andthe Group Ia or Ila metal or metal-containing materials can be combinedin any conventional manner which Will yield catalytic combinationssuitable for oxidative dehydrogenation processes. For example, thecatalyst components can be combined using a coprecipitation technique asdisclosed in detail hereinafter in the specific examples, byconventional aqueous or nonaqueous solution or suspension mixing, by ionexchange, by simply mixing the components by themselves without the useof additional solvents, and the like including combinations of thesetechniques.

Generally, the catalysts can be formed by mixing the components forperiods varying from about 1 minute to 5 hours in the presence orabsence of a solvent or dispersant, at temperatures from about roomtemperature up to about 200 F. Ambient, sub-ambient, or superambientpressures, and ambient or inert atmospheres such as nitrogen, and thelike can be used.

Suitable solvents or dispersants that can be employed for the combiningof the catalyst components include water, alcohol, or others for thestep of combining the tin compound and phosphorus compound, and thesesolvents as well as hydrocarbons, halogenated hydrocarbons, ketones,esters, and the like for any other steps of the catalyst preparation.

The catalyst itself when finished and in a condition for treatmentaccording to this invention will contain from about 0.1 to about 16weight percent phosphorous, from about 15 to about 75 weight percenttin, and from about 0.1 to about 10 weight percent Group Ia and/or IIametal, preferably 0.1 to 5 weight percent, all weight percentages beingbased upon the total weight of the final catalyst. The amounts ofphosphorus, tin, and Group Ia and/or IIa metal present in the finalcatalyst total less than 100 percent of the catalyst, the differencesbetween the total and the 100 percent being substantially combinedoxygen in sufiicient amount to satisfy the valence requirements of theGroup Ia and/or IIa metal, tin, and phosphorus.

A presently preferred method of preparing the catalyst to be treatedaccording to this invention is to mix solutions or suspensions of, forexample, the phosphates and/ or phosphoric acid, one or more tincompound, one or more Group Ia and/or IIa metal or compound, and atleast one of ammonia, ammonium hydroxide, sodium hydroxide and potassiumhydroxide, filter, wash to remove any undesirable electrolytes, dry, andcalcine. An agglomeration step such as pelletizing, extruding, orpilling, can precede or follow the drying step or calcining step.

The concentration of the various solutions that can be used to make thecatalyst to be treated according to this invention can vary widely,e.g., from about 0.01 to about molar or more, depending on thesolubility of the particular materials employed. Any order of mixing canbe used, and the final pH of the mixture is generally in the range offrom about 2 to about 10, preferably from about 3.5 to about 6.5. Theprecipitate that forms is separated from the liquid by any conventionalmeans such as filtration. Thereafter the precipitate is washed withdilute aqueous ammonium salt solutions such as ammonium acetate,ammonium nitrate, ammonium sulfate, and the like, and/ or with deionizedwater to remove electrolytes. The washed precipitate is then dried forfrom about 2 to about 24 hours at temperatures of from about 100 toabout 300 F. in air or an inert atmosphere such as nitrogen. The driedprecipitate is then calcined from about 1 to about 24 hours at fromabout 600 to about 1300 F., preferably at about the temperature at whichthe catalyst is to be used in the dehydrogenation process, under ambientor inert atmospheres. As mentioned before, an agglomerate-forming stepcan precede or follow the drying or calcining step. The dried andcalcined catalyst is preferably formed into to /2-inch pellets bycompression molding or extrusion, or is simply screened to a desiredsize, such as 1028 mesh (Tyler Sieve Series, Mechanical EngineersHandbook by L. S. Marks, 4th Edition, McGraw-Hill Book Co., Inc., N.Y.,1941, p. 836). Optimally a particulate tin/ phosphorus/ oxygen materialis formed, and the Group Ia and/0r IIa metal-containing compound orcompounds is added by, for example, impregnation followed by drying.

By this invention, these oxidative dehydrogenation catalysts are treatedby (a) heating the catalyst to 600 to 1300 F., preferably 1100 to 1200F., (b) impregnating the heated catalyst with a tin-containing materialto provide the catalyst with 0.25 to 10 weight percent of addiional tin,and (c) heating the treated catalyst at temperatures in the range of 600to 1300 F., preferably 1100 to 1200 F., in the presence of anoxygen-containing atmosphere.

Generally, the heating of step (a) is carried out for a time rangingfrom 1 to 24 hours. The heating of step (c) is carried out for a timeranging from 1 to 24 hours. If desired, the heating of step (a) can bethe final heating step of the original preparation of the oxidativedehydrogenation catalyst to be treated according to this invention.

The impregnation step can be carried out with any tincontaining materialwhich is converted by the subsequent heating step in anoxygen-containing atmosphere to tin oxide. For example, tin compoundssuch as stannous sulfate, stannic sulfate, stannous nitrate, stannicnitrate, stannous acetate, stannic acetate, stannous tartrate, stannictartrate, and the like can be employed. Preferably, stan nous sulfateand/or stannic sulfate are employed.

The improved catalysts of this invention can be used in any conventionaldehydrogenation, particularly oxidative dehydrogenation, process usingconventional procedures and techniques. Suitable oxidativedehydrogenation processes are those which dehydrogenate at least onematerial selected from the group consisting of alkenes, alkadienes,cycloalkenes, alkylpyridines, and alkyl aromatics, using an elevatedtemperature, and a molecular oxygen-containing gas, with or without thepresence of steam. The alkenes and alkadienes can contain from 3 to 10,preferably 4 to 6, carbon atoms per molecule, inclusive, and thecycloalkenes can contain from 4 to 10, preferably 4 to 6, carbon atomsper molecule, inclusive. The alkylpyridines and alkylaromatics cancontain from 1 to 4, preferably 1 to 2, alkyl groups per molecule whichthemselves contain from 1 to 6, preferably 4 to 6, carbon atoms pergroup, inclusive, with at least one alkyl group having at least 2 carbonatoms.

The advantages of this invention are further illustrated by thefollowing examples. The reactants and the proportions and other specificconditions are presented as being typical and should not be construed tolimit the invention unduly.

EXAMPLE Catalyst Preparations Catalyst 1 Aqueous solutions of stannicchloride and phosphoric acid were mixed and reacted with ammoniumhydroxide to give a precipitate. The precipitate was filtered and washedessentially free of chlorine by resuspension in water and refiltering.The washed precipitate was spraydried, mulled with about 5 percentwater, extruded to an extrudate 5 inch in diameter and about 4; inch inlength, and dried. The dried extrudate was impregnated with an aqueoussolution of lithium nitrate to give the final desired composition. Theimpregnated extrudate was dried and calcined at 1100" F. in air forabout 4 hours as the final preparation step. The final catalystcontained 10 percent phosphorus (22.9 percent P 0 and 58.4 percent tin(73.9 percent SnO The final composition also contained 1.5 percentlithium (3.2 percent Li O) Catalyst 2 Catalyst 1 was impregnated with anaqueous solution of stannous sulfate, dried, and calcined in air at 1100F. for 16 hours. The solution used to impregnate contained 3.6 grams ofSnSO in ml. of solution. The tin content was increased to 59.4 weightpercent as compared to Catalyst 1 which contained 58.4 weight percenttin. This was an inventive catalyst of the invention.

Catalyst 3 Catalyst 1 was impregnated with an aqueous solution ofstannous sulfate, dried, and calcined in air at 1100" F. for 16 hours.The solution used to impregnate contained 7.2 grams of SnSO- in 100 ml.of solution. The resultant tin content was increased to 60.4 weightpercent in this inventive catalyst.

Catalyst 4 Catalyst 1 was impregnated with an aqueous solution ofstannous sulfate, dried, and calcined in air at 1100 F. for 16 hours.The solution used for impregnation contained 14.4 grams of SnSOt, in 100ml. of solution. The resultant tin content was increased to 62.4 Weightpercent in this inventive catalyst.

Catalyst Testing I Physical strength (pounds of pressure required tocrush extrudates) as well as catalytic activity for dehydrogenation ofbutenes to butadiene are:

Conditions-Butane space velocity=300; air space velocity=l,200; steamspace velocity= 6,000; sample time in the dehydrogenation period= 3hours; pressure=atmospheric; quartz reactor; 7 mm. internal diameter; 3-4 in catalyst depth; 3-4 cc. of catalyst; product determination by gas11111912? gg rgmatography. Note, space yelocity is vol. of gas/vol. ofcatalyst/ No'rE.Yield=Mole percent of butenes converted to butadienesingle-pass; Modivity=5electivity to butadiene based ongas-phaseproducts only.

The above data demonstrate that the catalysts of this invention performas well as or better than the catalysts of the prior art. Further, thecatalysts of this invention clearly have improved physical strength overthe catalysts of the prior art.

Reasonable variations and modifications are possible within the scope ofthis disclosure without departing from the scope and spirit thereof.

I claim:

1. In an oxidative dehydrogenation process wherein at least onedehydrogenatable material selected from the group consisting of alkenes,alkadienes, cycloalkenes, alkylpyridines, and alkyl aromatics, iscontacted with a tin-phosphorus-oxygen-Group Ia or IIa metal catalystcomposition under oxidative dehydrogenation conditions, the improvementcomprising preparing said catalyst composition of increased physicalintegrity prepared by the process which comprises:

(a) combining under dehydrogenation catalyst forming conditionsefiective catalyst forming amounts of at least one phosphorus containingmaterial, at least one tin containing material, and at least one GroupIa or Group Ila metal containing material,

wherein said eflective catalyst forming amounts range from about 0.1 to16 weight percent phosphorus, from about 15 to 75 weight percent tin,and from about 0.1 to 10 weight percent Group Ia or Group He. metal,

at least one of said phosphorus, tin, and Group Ia or Group IIa metalcontaining materials contain oxygen, none of said materials aredeleterious to dehydrogenation catalytic effects, and all of theelements in said materials other than phosphorus, tin, oxygen, and GroupIa or Group Ila metal are volatilized by heating the combination atleast to a temperature utilized in a dehydrogenation process or areremoved from the composition by washing with a liquid that isnondeleterious to the catalytic effects of the composition,

(b) heating said admixture to a temperature of about 600 to 1300 F.,thereby preparing an Sn/P/O/Ia or Ila composition,

(c) impregnating said Sn/P/O/Ia or IIa composition with a further tincontaining material characterized as a tin oxide or tin compoundconvertible on heating in an oxygen-containing atmosphere to tin oxidein an amount sufiicient to provide the composition with about 0.25 to 10weight percent of additional tin,

(d) heating the so-impregnated composition containing said furthertin-containing material at a temperature in the range of about 600 to1300 F., thereby preparing said catalyst composition of increasedphysical integrity, and

(e) contacting said dehydrogenatable material with said catalystcomposition of increased physical integrity.

2. A process according to claim 1 wherein said alkene or alkadienecontains 3 to 10 carbon atoms per molecule, said cycloalkene contains 4to 10 carbon atoms per molecule, and said alkyl pyridine or alkylaromatic contains 1 to 4 alkyl groups per molecule which alkyl groupseach contains 1 to 6 carbon atoms per group with at least one alkylgroup having at least 2 carbon atoms.

3. The process according to claim 2 wherein said material is a butene.

4. The process according to claim 3 wherein the oxidativedehydrogenation catalyst has a final composition containing from 58.4 to62.4 weight percent tin.

5. The process according to claim 4 wherein said composite containsabout 1.5 percent lithium.

6. In a process of dehydrogenation of an organic feed material'-selected from the group consisting of alkenes, alkadienes, cycloalkenes,alkyl pyridines, and alkyl aromatics capable of oxidativedehydrogenation which comprises contacting said feed material with acatalyst composite of P/Sn/O and at least one Group Ia or IIa metal,under oxidative dehydrogenation conditions,

wherein the improvement comprises employing a catalyst composite ofincreased physical integrity prepared by impregnating said P/Sn/O/Ia orIla metal composite with a further tin-containing material suflicient toprovide 0.25 to 10 weight percent of additional tin based on the weightof the initial catalyst, and heating the so impregnated composite at anelevated temperature in an oxygen-containing atmosphere, and thereaftercontacting said organic feed material, wherein said furthertin-containing material is a tin oxide or tin-containing materialconvertible to the oxide upon said heating in an oxygencontainingatmosphere.

7. The process of claim 6 wherein said P/Sn/O/Ia or IIa metal compositecomprises about 0.1 to 16 weight percent phosphorus, about 15 to 75weight percent tin, and about 0.1 to 10 weight percent of at least oneGroup Ia or Group IIa metal with said oxygen being present as combinedoxygen.

8. The process of claim 7 wherein the heating of the soimpregnatedcomposite is at a temperature of about 600 to 1300 F.

9. The process according to claim 7 wherein said alkene or alkadienecontains 3 to 10 carbon atoms per molecule, said cycloalkene contains 4to 10 carbon atoms per molecule, said alkyl pyridine or alkyl aromaticcontains 1 to 4 alkyl groups per molecule which alkyl groups eachcontain 1 to 6 carbon atoms per group with at least one alkyl grouphaving at least 2 carbon atoms.

10. The process according to claim 9 wherein said alkene or alkadienecontains 4 to 6 carbon atoms per molecule, said cycloalkene containsfiom 4 to 6 carbon atoms per molecule, said alkylpyridine oralkylaromatic contains 1 or 2 alkyl groups per molecule which containfrom 4 to 6 carbon atoms per alkyl group.

11. The process according to claim 9 wherein said further tin containingmaterial is a tin sulfate, tin nitrate, tin acetate, or tin tartrate.

12. The process according to claim 10 wherein said dehydrogenatablematerial is a butene.

13. The process according to claim 11 wherein said further tincontaining material is tin sulfate.

14. The process according to claim 12 wherein said oxidativedehydrogenation conditions include a contacting temperature of about 900to 1000 F., and a contacting 7 16. The process according to claim 1wherein said 3,557,238 Group Ia or IIa metal is lithium, and saidfurther tin- 3,640,901 containing material is a tin sulfate. 3,674,7063,274,283

References Cited UNITED STATES PATENTS Cunningham 260-680 E Walker260-680 E Box et a1. 260-6833 Bethell 260-680 E 5 PAUL M. COUGHLAN, IR.,Primary Examiner US. Cl. X.R.

20-290 V, 669 R, 680 E, 696

